I think the iPhone/iTouch/iPad as of now won't kill the PSP and won't touch the DS, now, Nintendo and Sony are looking really close at the market, Sony has the tech to launch a PSPhone, and Ninty can join forces with a cellphone company to make the DSPhone (just like Google did with HTC for the Nexus One), so that's not a problem for them...
We'll see the next-gen of handhelds if that's convenient or not for them according to the market...